In general terms elevator systems serve the purpose of transporting persons or items in the vertical direction. In order thereby to avoid hazards to the persons or items, safety monitoring systems are regularly deployed. These monitor the current operating conditions of the elevator system, for example with the aid of detecting safety function components, i.e. for example by means of data or signals from sensors or from control devices. For example, a speed of an elevator car, or a state of closure of doors of the elevator system, is monitored. In the event of a critical operating condition the safety monitoring system activates suitable activatable safety function components, such as, for example, a braking device or a capturing device for purposes of braking, that is to say stopping, the elevator car. Here the most stringent requirements are placed on the safety monitoring systems with regard to their reliability and security.
Conventional safety monitoring systems often employ a central safety monitoring unit, which is connected to a multiplicity of detecting safety function components, or activatable safety function components, which have been arranged at various positions within the elevator system. By way of example, a detecting safety function component can be understood to mean, for example, a sensor or an output interface of a control device, which can determine and output signals or data that provide information on a current operating condition within the elevator system. An activatable safety function component can be understood to be, for example, an actuator, a motor, or similar, which can actively influence a current operating condition within the elevator system. Here signals or data, e.g. from sensors, will have been transmitted in each case to the central safety monitoring unit and processed there. If it has been recognized on the basis of processed results that, for example, a safety critical operating condition prevails in the elevator system, the central safety monitoring unit will have appropriately controlled one or a plurality of the activatable safety function components in order to ensure the safety of the elevator system and in particular of the persons being transported. For example, a braking or capturing device will have been activated when an excessive speed of the elevator car has been detected. Signals or data generated by sensors will have been transmitted unprocessed to the central safety monitoring unit, processed exclusively there, and then, based on the processed results, control signals will have been generated, which will have been sent to the activatable safety function components, in order to activate the latter in a suitable manner.
However, such a centrally monitored and controlled system regularly requires highly complex wiring. In addition, significant signal propagation times can occur between the locally provided detecting and activatable safety function components and the centrally provided safety monitoring unit, whereby the reaction times required by the safety monitoring system in order to react adequately to a critical situation that has occurred can be considerably lengthened. In addition, transmission of signals and data, for example from a multiplicity of distributed sensors to a single central safety monitoring unit and central data processing taking place there, can lead to significant processing times and thus can lengthen the reaction times further.
EP 2 022 742 A1 therefore proposes an elevator system with a decentralized control system. The decentralized control system has a plurality of evaluation units, wherein signals can be transmitted via bus connections between the evaluation units. Compared with centralized systems, this can reduce the wiring complexity and can shorten reaction times.
US 2011302466 A1 describes an elevator system with a safety monitoring system for purposes of monitoring safety function components. The safety monitoring system has a master unit and many slave units. The slave units are each assigned sensors and switches and receive signals, which they transmit to the master unit in a particularly well secured method. The master unit processes these data and activates, as appropriate, suitable safety function components, for example for stopping the elevator car.